In current company/enterprise networks, modern applications such as voice over IP (VOIP) calling, videoconferencing, media streaming and virtualized applications require low latency and other stringent quality of service (QOS) constraints. Bandwidth requirements are also increasing, especially for applications featuring high-definition (HD) video. Such varying quality of service requirements in turn drive traffic prioritization requirements to ensure that data for applications requiring a higher quality of service receive priority treatment in order to deliver a certain minimum level of performance to the data flow. For example, a required bit rate, delay, jitter, packet dropping probability and/or bit error rate may be necessary for an application to operate at an acceptable performance level. Depending on the type of network, however, delivering the necessary quality of service requirements poses significant challenges.
In high performance broadband communications networks, certain protocols or services can be offered that support the quality of service requirements of high priority, real-time traffic applications. For example, multiprotocol label switching (MPLS) is a current service offering in such high performance networks (e.g., in T1/E1, ATM Frame Relay and DSL networks), which supports quality of service requirements of such applications. MPLS directs data from one network node to the next based on short path labels, rather than long network addresses (e.g., the Internet), avoiding complex lookups in routing tables. MPLS services generally are significantly more expensive than the more typical consumer and small business Internet services, and thus can be cost prohibitive. Alternatively, constant or guaranteed minimum bit rate services are also available, and can solve quality of service requirements of real-time applications, but such services are similarly cost prohibitive. Public broadband wide-area networks (WANs), such as the Internet, on the other hand, present various advantages over such dedicated private lines, such as cost advantages (including both equipment and service cost advantages), and a wide variety and availability of standard networking devices (e.g., modems, routers, virtual private network (VPN) gateways and routers). WANs allow enterprises/companies to extend their computer networks over large distances, to connect remote branch offices to data centers and each other, and deliver the applications and services required to perform business functions. Accordingly, considering the advantages of such public WANs, there is a compelling desire by enterprises to use such public broadband WANs (Internet services) as the transport for their private networks.
A software-defined WAN (SD-WAN) can be employed, which simplifies the management and operation of a WAN by decoupling the networking hardware from its control mechanism, and thereby makes Hybrid WANs more practical. An SD-WAN is a hybrid WAN that is controlled via software, where the SD-WAN software manages the edge routers and offers more flexibility than the protocols built into standard routers. For example, an SD-WAN can allow more traffic to traverse the less-costly public broadband side of the network (the Internet) and dynamically route packets to the private side when needed. SD-WAN products are designed to address such networking problems by enhancing or even replacing traditional branch routers with virtualization appliances that can control application-level policies and offer a network overlay, whereby less expensive consumer-grade Internet links can act more like a dedicated circuit. SD-WAN products can be physical appliances or virtual appliances, and are placed in small remote and branch offices, larger offices, corporate data centers, and increasingly on cloud platforms. A centralized controller is used to set policies and prioritize traffic. The SD-WAN takes into account these policies and the availability of network bandwidth to route traffic, which helps ensure that application performance meets QOS and service level agreement (SLA) requirements.
With SD-WAN technology, different types of networks can be utilized to address QOS requirements. For example, different types of traffic can be routed over respective networks of different technologies and protocols to address the QOS requirements of each specific traffic type (e.g., critical traffic can be routed over a dedicated MPLS network, and less important traffic over a less expensive network—such as a broadband network or a wireless LTE network. Further, while SD-WAN products and services vary by vendor, many enable hybrid WAN connectivity—dynamically routing traffic over both private and public links, such as leased MPLS links and broadband, Long Term Evolution (LTE) and/or wireless. An SD-WAN architecture allows administrators to reduce or eliminate reliance on expensive leased MPLS circuits by sending lower priority, less-sensitive data over cheaper public Internet connections, reserving private links for mission-critical or latency-sensitive traffic like VOIP.
Unlike single-owner networks, the Internet is a series of exchange points interconnecting private networks, owned and managed by a number of different network service providers. The architecture and general protocols of packet switched networks (such as the Internet), however, are far less reliable than the more expensive high performance private broadband communications networks. As a series of exchange points interconnecting private networks owned and managed by a number of different network service providers, the behavior of the Internet is unpredictable. In packet-switched networks (such as the Internet), quality of service is affected by various factors, such as: (1) low throughput, whereby, due to varying load from other users sharing the same network resources (e.g., congestion), the bit rate provided to a certain data stream may be too low if all data streams get the same scheduling priority; (2) dropped packets, whereby a router may fail to deliver packets (e.g., where the packet is corrupted or the routers buffers are full); (3) bit errors, whereby a packet may be corrupted by noise or interference; (4) latency, whereby a packet is delayed in reaching its destination (e.g., based on long queues or long routes due to congestion); (5) jitter, whereby packets from one source/application reach the destination with different delays, which delays can vary unpredictably and cause jitter; and (6) out-of-order packet delivery, whereby related packets from a single source/application are routed through a network over different paths and thus experience differing levels of delay resulting in the packets arriving at the destination in a different order from which they were sent (which requires special additional protocols responsible for rearranging out-of-order packets).
Additionally, conventional Internet routers and local area network (LAN) switches operate on a best effort basis, which generally does not support quality of service. Under a best effort delivery service, the network does not provide any guarantees for timing and order of data packet delivery, or any guarantees of data packet delivery at all—and thus do not generally provide any guaranteed quality of service or priority levels. In a best effort network, generally, all users obtain best effort service, meaning that they obtain unspecified variable bit rate and delivery time, depending on the current traffic load. The lack of reliability permits various error conditions, such as data corruption, packet loss and duplication, as well as out-of-order packet delivery. Since routing is dynamic for every packet and the network maintains no state of the path of prior packets, it is possible that some packets are routed on a longer path to their destination, resulting in improper sequencing at the receiver. Such networks, therefore, are generally unreliable for real-time applications, such as VOIP.
A Hybrid WAN can be employed to connect a geographically dispersed wide area network (WAN). A Hybrid WAN connects a geographically dispersed wide area network (WAN) by sending traffic over two or more sequential connection types (e.g., a hybrid WAN may employ dedicated multiprotocol label switching (MPLS) circuits plus carrier Ethernet plus T3 links). More recently, hybrid WANs have evolved to encompass traditional leased lines in concert with public Internet connections. By using this approach, a hybrid WAN can give organizations a more versatile and cost-effective way to connect their offices while still relying on dedicated links to send mission-critical data. A Hybrid WAN may extend enterprise networks across networks of multiple carriers, and thus face they face operational challenges including network congestion (e.g., brownouts), jitter, packet loss, and service outages (blackouts). Further, complexities relating to management and troubleshooting can render it prohibitively expensive difficult to expand WAN capabilities. Further, broadband Internet access suffers more complete outages (blackouts) and periods of time of poor quality of service (brownouts) than private lines.
What is needed, therefore, is an approach for a secure private networking solution that achieves improved network availability in enterprise Hybrid WAN networks, and facilitates support of application-level quality of service traffic requirements of enterprise applications, and which is more cost effective than private networking solutions that employ dedicated circuits.